Interpretive Summary: Omega gliadins comprise between 5 and 10% of wheat flour protein and are unusual in that they consist almost entirely of repetitive sequences. In addition, some of these proteins have been shown to be responsible for important food allergies. DNA sequences for omega gliadins expressed in a US bread wheat variety were identified in public databases. The sequences of the proteins encoded by the genes suggest that different omega gliadin proteins may play distinct roles in flour quality. Based on these sequences, quantitative methods were developed to evaluate the effects of fertilizer applications on the expression of two different types of omega gliadin genes during grain development. The study revealed that omega gliadin gene expression was enhanced by fertilizer, resulting in higher levels of omega gliadin transcripts in grains that received fertilizer than in those that did not. These studies are important because changes in the levels of omega gliadins may influence flour quality and allergenicity.

Technical Abstract:
The partial coding sequences of omega gliadin genes expressed in developing wheat kernels Triticum aestivum cv Butte 86 were identified in EST databases. Three gene assemblies encode proteins with PQQPFP as the predominant repetitive motif. Of these, two encode proteins with at least one cysteine and thus may be incorporated into the glutenin polymer. Another two gene assemblies encode proteins with FPQQQ and QQIPQQ repeats. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was used to investigate the accumulation of omega gliadin transcripts in developing wheat grains produced with or without post-anthesis fertilizer supplied as 20-20-20 NPK. Transcripts for both types of proteins were detected at 8 DPA. The levels of transcript changed little in the absence of post-anthesis NPK during grain development, but increased when plants were supplied with post-anthesis NPK. By 32 DPA, levels of omega gliadin transcripts were considerably higher in grains that received NPK than in those that did not receive NPK. Transcripts for a gamma gliadin showed a different profile, increasing from 8 to about 22 DPA, then decreasing at later time points. In contrast to omega gliadins, both the timing and levels of gamma gliadin transcripts were similar in grains produced with or without post-anthesis NPK.